diff --git a/Part 1 - Getting Started/2. Key types.md b/Part 1 - Getting Started/2. Key types.md
index 12ac033..1b98c3e 100644
--- a/Part 1 - Getting Started/2. Key types.md	
+++ b/Part 1 - Getting Started/2. Key types.md	
@@ -45,7 +45,7 @@ When developing Rx code, you'll see a lot of `Observable`, but not so much of `O
 
 ## Implementing Observable and Observer
 
-You could manually implement `Observer` or extend `Observable`. In reality that will usually be unnecessary, since Rx already provides all the building blocks you need. It is also dangerous, as interaction between parts of Rx includes conventions and internal plumming that are not obvious to a beginner. It is both simpler and safer to use the many tools that Rx gives you for generating the functionality that you need.
+You could manually implement `Observer` or extend `Observable`. In reality that will usually be unnecessary, since Rx already provides all the building blocks you need. It is also dangerous, as interaction between parts of Rx includes conventions and internal plumbing that are not obvious to a beginner. It is both simpler and safer to use the many tools that Rx gives you for generating the functionality that you need.
 
 To subscribe to an observable, it is not necessary to provide instances of `Observer` at all. There are overloads to `subscribe` that simply take the functions to be executed for `onNext`, `onError` and `onSubscribe`, hiding away the instantiation of the corresponding `Observer`. It is not even necessary to provide each of those functions. You can provide a subset of them, i.e. just `onNext` or just `onNext` and `onError`.